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Autoregulation of topoisomerase I expression by supercoiling sensitive transcription

Ahmed, Wareed and Menon, Shruti and Karthik, Pullela VDNB and Nagaraja, Valakunja (2016) Autoregulation of topoisomerase I expression by supercoiling sensitive transcription. In: NUCLEIC ACIDS RESEARCH, 44 (4). pp. 1541-1552.

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Official URL: http://dx.doi.org/10.1093/nar/gkv1088

Abstract

The opposing catalytic activities of topoisomerase I (TopoI/relaxase) and DNA gyrase (supercoiling enzyme) ensure homeostatic maintenance of bacterial chromosome supercoiling. Earlier studies in Es-cherichia coli suggested that the alteration in DNA supercoiling affects the DNA gyrase and TopoI expression. Although, the role of DNA elements around the promoters were proposed in regulation of gyrase, the molecular mechanism of supercoiling mediated control of TopoI expression is not yet understood. Here, we describe the regulation of TopoI expression from Mycobacterium tuberculosis and Mycobac-terium smegmatis by a mechanism termed Supercoiling Sensitive Transcription (SST). In both the organisms, topoI promoter(s) exhibited reduced activity in response to chromosome relaxation suggesting that SST is intrinsic to topoI promoter(s). We elucidate the role of promoter architecture and high transcriptional activity of upstream genes in topoI regulation. Analysis of the promoter(s) revealed the presence of suboptimal spacing between the -35 and -10 elements, rendering them supercoiling sensitive. Accordingly, upon chromosome relaxation, RNA polymerase occupancy was decreased on the topoI promoter region implicating the role of DNA topology in SST of topoI. We propose that negative supercoiling induced DNA twisting/writhing align the -35 and -10 elements to facilitate the optimal transcription of topoI.

Item Type: Journal Article
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Additional Information: Copy right for this article belongs to the OXFORD UNIV PRESS, GREAT CLARENDON ST, OXFORD OX2 6DP, ENGLAND
Department/Centre: Division of Biological Sciences > Microbiology & Cell Biology
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Date Deposited: 07 Apr 2016 07:27
Last Modified: 07 Apr 2016 07:27
URI: http://eprints.iisc.ernet.in/id/eprint/53624

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